Conversion of hydrocarbons

ABSTRACT

ACID MORDENITE, A CRYSTALLINE ALUMINOSILICATE HAVING A RATIO OF SILICON ATOMS TO ALUMINUM ATOMS OF ABOUT 5 TO 1 CAN BE USED AS A CATALYST FOR VARIOUS HYDROCARBON CONVERSION PROCESSES, INCLUDING ISOMERIZATION OF NAPHTHENES.

3,597,493 CONVERSION OF HY DROCARBONS Vincent J. Frilette, Yardley, andMae K. Rubin, Bala Cynwyd, Pa., assignors to Mobil Oil Corporation NoDrawing. Continuation of application Ser. No. 494,228, Oct. 8, 1965,which is a continuation of application Ser. No. 142,778, Oct. 4, 1961.This application Jan. 15, 1968, Ser. No. 697,610

Int. Cl. C07c /22 U.S. Cl. 260-666 14 Claims ABSTRACT OF THE DISCLOSUREAcid mordenite, a crystalline aluminosilicate having a ratio of siliconatoms to aluminum atoms of about 5 to 1 can be used as a catalyst forvarious hydrocarbon conversion processes, including isomerization ofnaphthenes.

CROSS REFERENCES TO RELATED APPLICATIONS This application is acontinuation of application Ser. No. 494,228, filed Oct. 8, 1965, which,in turn, is a continuation of application Ser. No. 142,778, filed Oct.4, 1961, both now abandoned.

FIELD OF INVENTION The invention relates to various hydrocarbonconversion processes which may be catalyzed by acid mordenite.

DESCRIPTION OF PRIOR ART This application contains certain claims whichhave been copied from U.S. Pat. 3,299,153.

SUMMARY OF INVENTION The invention is directed to a wide variety ofhydrocarbon conversion processes, e.g., cracking, reforming,disproportionation, isomerization, alkylation, etc., wherein acrystalline aluminosilicate catalyst is employed. The catalyst is acidmordenite, a crystalline aluminosilicate.

This invention has to do with the catalytic conversion of hydrocarbonsand is particularly concerned with carrying out such conversions over acatalytic material of unique capabilities.

Zeolitic materials, both natural and synthetic, in naturally occurringand modified forms have been demonstrated as having catalyticcapabilities for hydrogen conversion. Such zeolitic materials areordered crystalline aluminosilicates having definite crystallinestructure Within which there are passages, pores, or cavities ofdefinite ranges of size. Since the dimensions of these pores are such asto accept for adsorption molecules of certain dimensions while rejectingthose of larger dimension, these materials have been referred to asmolecular sieves and utilized in many ways taking advantage of theseproperties.

A newly investigated zeolitic material is mordenite. Mordenite is anordered crystalline alumino-silicate, having a ratio of silicon atoms toaluminum atoms of about 5 to 1. It occurs naturally and has also beensynthesized. It occurs usually as the sodium salt and corresponds to theformula:

Nag 3 40241320 The ordered alumino-silicate crystalline framework ofmordenite differs from that of other known zeolites in that it iscomposed of chains of S-membered rings of tetrahedra and its porosityindicates one parallel system of channels having free diameters of theorder of 4 A.- to 6.6 A., interconnected by smaller channels, parallelto another axis of the order of 2.8 A. free diameter.

This invention is specifically concerned with various conversions ofhydrocarbons in the presence of activated United States Patent 0" "icemordenite and its applications to hydrocarbon conversions as its object.Other objects are in part obvious and in part appear hereinafter.

The unique catalyst with which this invention is concerned may beprepared by the activation of naturally occurring mordenite. One methodof preparation is to reduce the material to a fine powder, at leastpassing the standard 200-mesh sieve, and preferably passing BOO-mesh or325-mesh standard sieves, or finer, followed by acid treatment. Aspecific example of acid treatment is to contact 10 grams of a powderedmordenite passing a 325- mesh sieve with to 200 ml. of 0.1 N HCl for 15minutes, filter, and repeat, then treat with 125 to 200 ml. of 1.2 N HClfor 15 minutes, and repeat (all at room temperature), followed byrinsing until filtrate shows no acidity. The filter cake, dried at 120C. and pelleted, will yield about 8 grams of catalytic material.

Such treatment as above outlined Will result in an activated mordeniteat least 50% of which is in the H or acid form. Since the presence ofalkaline earth metal ions in the ordered crystalline structure sometimesis found to confer a degree of stability, such materials may be present.If the naturally occurring mordenite contains calcium, as it frequentlydoes, the acid treatment may be so handled as to leave a portionpresent, or the alkaline earth metal ions may be introduced by baseexchange in known manner. However, the amount of calcium or similarsubstitution should be carefully controlled and held to values such asdo not materially alter the conversion capabilities of the catalystwhich should be at least 5 0% in the acid or H form.

Also, the material may be treated in known manner to incorporate certainactive trivalent metals, such as cerium, lanthanum, iron, and the like,capable of modification of the catalytic reactions.

Similarly, the proportion of aluminum, in the trivalent form, may beincreased, with significant alteration in the catalytic activity of thematerial for many reactions.

Such a catalyst is capable of adsorbing carbon dioxide to the extent ofabout 10% of its own weight. It is further and most strikinglycharacterized by a capability of converting normal hexane to the extentof about 20 weight percent at a temperature of 240 C. (465 F.) and apartial pressure of about mm. in the presence of an inert gas, at aliquid hourly space velocity of about 0.5 in a tenminute duration run infixed bed operation.

To further characterize this catalytic material, it has a surface areain the H form of 300 m. gm. and above.

It is thermally stable upon repeated exposure (e.g. regenerations) totemperatures of the order of 600 C. (1,1l0 F.) and even up to about 800C. (1470 F.) under certain conditions.

Summarizing these properties, when the term catalyst of theacid-activated mordenite type is used hereinafter, that term refers to amaterial:

(1) Having an atomic ratio Si/Al of about 5/ 1.

(2) Having the crystalline structure of mordenite as shown by powderX-ray diffraction.

(3) Having the acid or H form, or not more than about 50% as a partialsalt thereof.

(4) Having a surface area of at least 300 m. /gm.

(5) Thermally stable.

(6) Capable of converting hexane to the extent of about 20 weightpercent at a temperature of 240 C. and a partial pressure of about 150mm. in the presence of an inert gas, at a liquid hourly space velocityof about 0.5 in a run of ten minutes duration in a fixed bed operation.

HYDROCARBON CRACKING As an example of the high and unexpected capabilityof this catalyst of the acid-activated mordenite type, reference is madeto the conversion of normal hexane. In the presence of a conventionaltype of silica-alumina catalyst, amorphous in nature, of an activityindex of 46, hexane is stable until temperatures of the order of 500 C.(930 F.) are reached.

In contrast, when passed in contact with the present catalyst, hexaneundergoes substantial conversion at 240 C. (435 F.), in a lowconcentration in inert gas carrier.

While it is known that crystalline alumino-silicates: are more activethan the amorphous forms, the present catalyst is more active than theusual crystalline aluminosilicates. =In contrast to the substantialconversion of hexane at 240 C. (435 F.) noted above for this catalyst,the acid form of the Y variety of faujasite does not exhibit conversionof hexane until temperatures of about 330 C. (625 F.) are reached.

A further notable characteristic of the conversion of parafiinicmaterials over this catalyst is the nature of the products ofconversion. With hexane charge, there are no 0,, olefins or lowerolefins produced, the effluent products being saturated, and asubstantial portion of those products-form 40-60% of them-beingisobutane and isopentane. Some isohexane also may be produced. Alsonotable is the fact that dry gas, that is, methane and ethane, is notproduced in detectable quantities.

This conversion, in the production of iso-compounds, the absence ofmethane and ethane, the indicated ability for hydrogen transfer,resembles the conversions accomplished over catalysts of the type ofA101 rather than those usually associated with silica-alumina catalysts.

At higher temperatures, the product distribution changes. With hexanecharge, at about 410 C. (770 F.), hexane is highly converted, andolefins, toluene, and benzene appear in the product. The appearance ofaromatics indicates a reforming capability of this catalyst, and that ata temperature about 100 C. lower than those usually utilized forreforming over platinum catalysts.

Conversion of normal heptane over this catalyst behaves similarly,except that conversion sets in at the lower temperature of 180 C. (355F.), and aromatic compounds appear in the products of conversion attemperatures of about 300 C. (575 F.), heptane being almost whollyconverted at temperatures of about 320 C. (610 F.).

It will be realized from the above data that this catalyst presents aunique utility not only for the cracking of normal petroleum fractions,but for the reforming of naphthas of low anti-knock capability toproduce products of higher anti-knock value. The C cut of normallyproduced gasolines, composed mainly of hexane, but also containingsignificant quantities of pentane and heptane is ordinarily considered asomewhat difficult thing to handle in upgrading 'and in some casesresort is had to very high temperature thermal cracking to destroy itwith the production of ethylene, propylene, and other fragments whichthen may be tailored into effective antiknock components or divertedinto profit channels other than gasoline.

With this present catalyst, this fraction can be converted to desirableproduct at relatively low temperatures.

For example, in a fixed bed operation conducted at temperatures of theorder of 400-420 C. (750-800 F.), at a space velocity of the order of.0.5 (liquid volume charge at 20 C./volume occupied by catalyst, at apartial pressure of about 150 mm. in the presence of inert gas, and fora 10-minute duration of cracking portion of the cycle, in excess of 50%(weight percent) of a material composed mainly of hexane will beconverted to toluene, benzene, iso-compounds, and olefins suitable foralkylation.

The regeneration of this catalyst is readily accomplished with air attemperatures of 300 C. (575 F.), and up wards to about 600 C. (1110 F.).

Thus, the catalyst lends itself readily to any form of cyclic process inwhich it is alternately exposed to conversion of a charge and toregeneration.

4 CONVERSION OF CYCLO'PARAFFINS TAB LE I Conversion products (wt. Duringthat percent) minute Minute on methylstream cyclopentane Other Total d10. 7 2. 6 13. 3 37th 11. 1. 6 12. 8 134th l1. 0 1. 1 12. 1 164th 11. 50. 9 12. 4

The continued conversion ability of the catalyst under these conditionsis of considerable significance.

In a similarly conducted experiment with methyl cyclohexane atincreasing temperatures, the following was noted.

TABLE II Wt. percent methylcyclohexane Temp. C.: converted 250 (482 F.)7.4 320 (608 F.) 29 370 (680 F.)

At the highest temperature, the products included dimethylcyclopentanesand aromatics.

BENZENE CONVERSION It has been found that the catalytic conversion ofbenzene to other products such as toluene and ethylbenzene can beaccomplished at reasonable temperature levels over this catalyst ofacid-activated mordenite type.

This is somewhat unusual in that benzene would not normally beconsidered a compound which would undergo transformation over oxidecatalysts. In the usual case, over amorphous catalytic materialscomposed of silicaalumina complexes, benzene appears to be a relativelyquite stable product, as, for example, in the cracking of petroleumhydrocarbons.

Nevertheless, with the present catalyst, the production ofalkylaromatics begins with the appearance of toluene in the products oftreatment at about 375 C. (689 F.) with ethyl benzene appearing at about450 C. (846 F.), and in increasing amounts as the temperature isincreased, until, in passing over a fixed bed of this catalytic material at a temperature of about 525 C. (977 F), about 16 weight percentof the benzene fed appears as toluene and ethylbenzene.

ALKYLATION OF BENZENE Alkylation of benzene may be conducted over thiscatalyst of acid-activated mordenite type at relatively conservativetemperature levels, and in vapor phase or liquid phase as appropriatefor the temperature conditions used.

For example, in vapor phase, ethylene and benzene may be passedtogether, with benzene in excess, to produce ethyl benzenes and otheralkyl benzenes. With about 2/1 mol proportions of benzene and ethylene,ethyl benzene is produced at about C. and appears in significantquantities beginning at about C. (300 F.) at atmospheric pressure. Theamount of benzene converted to alkyl benzenes follows a temperaturepattern in accord-,

ance with the following.

TABLE III Wt. percent benzene Temp. C.: converted 152 4.2 162 4.2 2406.2 383 (721 F.) 14.6

In addition to ethyl benzene, and particularly at the highertemperatures, the efiluent was found to contain diethyl benzene,o-xylene, cumene, and some toluene.

The above experiments were carried out with a stream of helium ascarrier gas, saturated with benzene at atmospheric temperature andpressure, to which the desired amount of ethylene had been added.

Similarly, but in liquid phase, alkylation of benzene with propylene isfound to proceed readily in liquid phase at temperatures of about 78 C.(175 F.) with the production of cumene. Benzene was provided in excess.The catalyst used was the dried powder form, slurried into the reactionmixture, this mixture being gotten by flowing propylene in vapor forminto a body of benzene. The rate of production of cumene was found to beabout 0.84 mmols cumene/hour/ gram of catalyst at 78 C.

TOLUENE DISPROPORTIONATION This catalyst of the acid-activated mordenitetype exhibits a high capability for the disproportionation of toluene,as shown by the following data.

TABLE IV Disproportionation of toluene at 300 C. (572 F.)

Conversion during that Minute on stream: period, wt. percent 2427 incl.47.3 62-68 incl. 46.4 73-77 incl. 38.6 91st 33.0 120th 30.0 170th 24.3

The liquid hourly space velocity of this operation was about .04, at atoluene partial pressure of about 20 mm. in a stream of helium carriergas. The products were mainly Xylenes and benzene, and no evidence oflight fragments was detected.

In contrast, passing toluene over an amorphous silicaalumina catalyst of46 Activity index, only about 2% conversion can be had at 546 C. (1013F.).

INTERCEPTION OF CRACKING BY ALKYLATION It was noted earlier in thisspecification that, while the cracking of parafiins at lowertemperatures over this catalyst of acid-activated mordenite type did notgive rise to olefins, at higher temperatures, olefins were formed. Ithas also been noted that alkylation of benzene with olefins is possibleat relatively low temperatures over this catalyst.

This combination of capabilities gives rise to an interestingconversion, wherein a paraffin, such as heptane is cracked over thiscatalyst at conversion temperatures in the presence of an alkylatablematerial such as benzene.

The course of such treatment with temperature is shown by the following:

TABLE V.NHEPTANE CRACKING IN PRESENCE OF BENZENE Benzene Heptane cnv.,wt. eonv., wt. Temp., 0 percent percent 0 7 Cracked products. 0 21 Do.3. 6 47 Do. 6. 1 92 Cracked products plus toluene,

ethyl benzene, oxylene. 360 (680 F.) 21. 0 95 Cracked products plustoluene,

xylene, diethylbenzene.

From the above, it will be noted that a very substantial conversion ofthe type noted occurs. This is particularly significant when consideringthe capability of this catalyst for reforming type operations,particularly noting that according to Table III, with benzene present,the formation of alkyl benzenes becomes significant at temperatures ofthe order of (C.

OLEFIN POLYMERIZATION This catalyst of the acid activated mordenite typehas also been found to be quite active for the polymerization ofolefins. For example, passing ethylene over this catalyst attemperatures of around 200 C. (392 F.) gives rise to an oily polymerliquid and some ethane, but little C to C hydrocarbons.

This polymerization of olefins occurs over a wide temperature range,beginning at temperatures of the order of ambient temperatures.

From the above summary of various, it is evident that this catalyst ofthe acid-activated mordenite type possesses quite interesting, unusual,and very significant capabiilties.

What is claimed is:

1. An improved process for isomerizing naphthenic hydrocarbons whichcomprises subjecting said naphthenic hydrocarbons to isomerizationconditions in the presence of a catalyst comprising a crystallinemordenite zeolite.

2. The process of claim 1, wherein said mordenite zeolite has been baseexchanged with a hydrogen-containing cation.

3. The process of claim 1, wherein said isomerization conditions includea temperature within the range of about 350 to about 800 F., a pressurewithin the range of about 0 to about 1000 p.s.i.g., and a catalystcharge within the range of about 0.2 to about 5 volumes of feed pervolume of catalyst per hour of reaction time, said conditions beingselected to maintain the proportion of cracked products below about 20wt. percent, based on feed.

4. The process of claim 1, wherein said naphthenic hydrocarbons comprisecyclohexane.

5. An improved process for isomerizing naphthenic hydrocarbons whichcomprises subjecting a feed containing said naphthenic hydrocarbons toisomerization conditions in the presence of a catalyst comprising acrystalline mordenite zeolite having a silica to alumina mole ratio ofabout 9 to 11 and containing less than about 5.0 Wt. percent Na O.

6. The process of claim 5, wherein said mordenite zeolite has beensubjected to base exchange with a hydrogencontaining cation to reduceits Na O content.

7. The process of claim 5, wherein said isomerization conditions includea temperature of about 400 to 600 F., and a pressure of about 0 to 400p.s.i.g., and wherein the proportion of cracked products is maintainedbelow about 20 wt. percent, based on feed.

8. An improved process for isomerizing naphthenic hydrocarbons whichcomprises subjecting said naphthenic hydrocarbons to isomerizationconditions in the presence of a catalyst comprising a crystallinesynthetic mordenite zeolite.

9. The process of claim 8, wherein said mordenite zeolite has been baseexchanged with a hydrogen-containing cation.

10. The process of claim 8 wherein said isomerization conditions includea temperature within the range of about 350 to about 800 F., a pressurewithin the range of about 0 to about 1000 p.s.i.g., and a catalystcharge within the range of about 0.2 to about 5 volumes of feed pervolume of catalyst per hour of reaction time, said conditions beingselected to maintain the proportion of cracked products below about 20wt. percent, based on feed.

11. The process of claim 8, wherein said naphthenic hydrocarbonscomprise cyclohexane.

7 12. An improved process for isomerizing naphthenic hydrocarbons whichcomprises subjecting a feed containing said naphthenic hydrocarbons toisomerization conditions in the presence of a catalyst comprising acrystalline synthetic mordenite zeolite having a silica to alumina moleratio of about 9 to 11 and containing less than about 5.0 wt. percent NaO.

13. The process of claim 12, wherein said mordenite zeolite has beensubjected to base exchange with a hydrogen-containing cation to reduceits Na O content.

14. The process of claim 12, wherein said isomerization conditionsinclude a temperature of about 400 to 600 F., and a pressure of about 0to 400 p.s.i.g., and wherein the proportion of cracked products ismaintained below about 20 wt. percent, based on feed.

References Cited UNITED STATES PATENTS US. Cl. X.R.

